Aircraft heater



Patented July 4,

1 UNITED STATES PATENT OFFICE issguz I sanie smshsamirmnkusalabuimmmore,N. Y., assignorstoBcll Aircraft tion, Buffalo, N. Y.

Corpora- Application December 12, 1940, Serial No. 369,828- 7 2 Claims.(01. 237-123) This invention relates to aircraft heaters, and

more particularly'to devics' adapted to efhcientply heat closedcompartments of aircraft, or the like, when operating at relatively highaltitudes.

More specifically the invention relates to-a. combustion type of heatertaking its supply of fuel from the fuel mixing apparatus of the aircraftengine;

One of the objects of the invention vide a heater of the characterdescribed which is adapted to utilize fluid pressure differentialconditions at opposite points in the system in an istopro-' improvedmanner to provide propulsion of fluid fuel into the heat exchangeportion thereof. Another .object is to. provide a heater of thecharacter described which is adapted to hmction in an improved mannerand efiectively under relatively high altitude conditions. Anotherobject.

of the invention is to provide-a simplifled'automatic control system fora heater apparatus having the above described capabilities. Otherobjects and advantages of the invention will appear from thespecification hereinafter. a

We areawarethat combustion. 't'ype heaters have been previously devisedwhich operate upon the principle of vapor fuel circulation into thecombustion chamber as the result ofconnecting the discharge portion ofthe combustion chamber to a conduit which is under reduced pressureor'partial vacuum. In such cases the jected to surrounding atmosphericpressures.

Hence, such types of heaters will operate success- In the drawings; Fig.1 is a fragmentary schematic sideelevationofanairplanefuselageandengincshowingn invention in associationthere- Fig. 3isa wiring diagram of thecontrol mech-, r

anism thereof. The drawings illustrate the invention in association withan airplane fuselage d generally by the numeral ll having a compartmentwall l2 and floor H. The airplane engine is indicated at 16 and isequipped with a carburetor l8 and a supercharger blower indicated at 28;the blower 2|! being located between the carburetor l8 and the enginefuel intake manifold indicated at 22. The heater; indicated generally byth numeral. 2 is located below the compartment 'floor H and .is arrangedto take relatively cold air through a conduit 26 and to discharge theheated air into the compartment through means of a conduit 28; but itwill be understood that in lieu of the arrangement illustrated hereinthe heat exchange portion of the apparatus may be located at any otherdesired positionin the airplane. I

As better shown in Fig.2, the heat exchange element of the apparatuscomprises a box-like casing 30 arranged in open communication at. itsupper end with the air intake conduit 26 and at a lower end portionthereof in open communiiully at relatively low altitudes as inconnection with normal automobile use whenever-the discharge portion ofthe combustion chamber is connected in open communication with theautomobile intakemanifold or-some' other suitable source of partialvacuum. However, such heater and fuel circulating systems, while beinggenerally satisfactory for use in connection with automobiles and otherlow-altitude operating vehicles are entirely unsatisfactory andinefiectual at higher altitudes such as those at which modem airplanesoperate. The present inven- "tion, therefore, contemplates a method andheater is associated.

.tive circulation ofair from the intake conduit 26 through the casing 30and thence into the discharge conduit 28. Th control means for Y themotor 36 and the method of its functioning will be explained .more fullyhereinafter.-

' The heating element of the device is illustrated in Fig. 2 ascomprising a combustion chamber, 40 of elongate form'disposedsubstaniaally transversely ofthe'interior of the casing 3|! and 'in thepath of movement of air therethrough. The chamber 40 is-in the form of ahollow case prowith a. central horizontal partition 42 o as to providea'generally .U-shaped passageway for hot gases therethrough as indicatedby the thus caused to flow through the chamber in a 12; .The oppositeend of the igniter wire eletortuous path so as to provide increaseopporment is connected in series to a signal lamp II tunity for heatexchange action. The combusand from thence by means of a conductor intotion chamber 40 is mounted against a. perforated connection with a fixedcontact element of the side wall portion of the casing 30, and a header5 switch 80. Hence, whenever the switch 80 leadmember 50 is mounted atthe opposite side of the justed to heater-on position the circuitthrough casing wall so as to be in open communication the igniter 12 andthe signal lamp 85 is initially with the interior of the combustionchamber, closed.

thus providing a completely enclosed unit. Conductors leading to thewinding of a sole- The header member 50 is formed with an igninoiddevice 59 are shunted across the circuit tion chamber 52 arranged inopen cor'nmunlcaleading to the igniter. and signal lamp devices,

tion with the portion of the combustion chamber and the armature of thesolenoid device 59 is opinterior disposed above the partition 42, anderatively associated with the fuel control valve a fuel inlet conduit 54is mounted in connected 58 of the fuel inlet conduit 54 in such mannerrelation with the interior of the ignition cham- 15 that the latter isactuated by the solenoid device ber 52 so as to be adapted to conductheater to valve-open position whenever the heater switch fuel into theignition chamber. The conduit 54 80 is in heater-on position. Thus, uponclosis connected at its other end in communication ing of the switch 80subsequent to a 'period of with the interior of the engineintakemanifold non-operation, the solenoid 59 causes the valve 22 throughmeans of a suitable connection de- 58 to be opened to permit passage offuel vapor vice 56. A valve 58 is disposed in the line of from theintake manifold 22 through the conduit the conduit 54 for control of.passage of fuel 54 into the ignition chamber 52, and thence vaporthrough the heater feed conduit. through the combustion chamber 40 andinto the The header member 50 is also provided with discharge conduit 62leading to the engine fuel a discharge chamber 80 disposed in opencomfeed system. It will be understood that this mode municatlon with theinterior of the combustion of vapor fuel movement through the heater andchamber 40 below the partition 42 thereof so as conduit system will beautomatically provided by to be adapted to receive the gases issuingfrom reason of the difference 'between the pressures the combustionchamber subsequent to circulaexisting in the conduit system at the pointof tion therethrough. Agas discharge conduit 62 is fuel intakeconnection 55 and at the point of connected in open communication withthe chamdischarge into the conduit 52. ber 6i] by means of a suitableconnection nipple As fuel vapor moves into the conduit system device 64,and the conduit 62 is illustrated in Fig. as described hereinabove uponopening of the 1 as leading into open communication with the valve 58,the vapor passes adjacent the starting engine feed conduit '65 extendingfrom the enigniter 12 (which is then energized) and is thereginecarburetorWB to the engine supercharger by ignited. The resulting flamepasses into the blower 20. The conduit 62 is shown as being combustionchamber through'the igniter o'riconnected to the conduit '56 by means ofa confice, I0, and the latter is thereby heated to a tio d vice 68,temperature sufllcient to enable it to function to A fuel igniter 10 inthe form of an annulus of 40 provide continuous ignition of thefollowing refractory material is mounted in the fuel passtream of fuelvapor conducted into the combussageway between the ignition chamber 52and the tion chamber. During this initial combustion combustion chamber40, and a starting igniter period the temperature of the heat exchange12 in the form of an electrical resistance wire is structure of theapparatus will also be raised to a mounted upon the header in suchmanner as 45 temperature sufflcient to provide transmission oi to extendinto the path of the fuel-air vapor mixheat to. the bi-metallic element82 in such manture taken by the conduit il-ofr'om the engine ner as tocause it to become deformed and to manifold 22 as it passes through theignition lower its free end portion out of contact with chamber 52. ftt'he ignite wire I2 is connected ,the contact member 84 and intocontact with a in series with a source ofelectrical' energy as will socontact member 80 from which a conductor leads be more fully explainedher after and isvso to the fan motor 36 and from thence, into conformedas to be adapted t3" come sumciently nection with the conductor leadingto the flxed' heated by passage of an electrical current therecontactelement of the switch 80. through to provide for ignition of the fuelmix- Thus, upon attainment of operative temperature vapor entering thecombustion chamber. 55 tureswithin the heater structure the circuit Asillustrated by Fig. 3, the control mechathrough the starting igniter I2is automatically nism for the heat exchangeapparatus of the inop ned andthe fan]! is automatically brought:

vention includes an electrical circuit deriving eninto operation so asto produce circulation of air ergy from a battery as indicated, or anyother through the intake conduit 26 and against the suitable powersource. A pair of conductors exp combustion chamber case 4|, and thencethrough tend from opposite terminals of-the. power-source the outletconduit 2' into the airplane cabin. It and one of the' conductorsleads-to the movable 3 will also be understood that the signal lamp 5.element of a manually operable off-on switch inwill provide a visibleindicator at all times whendicated at 80. The switch 55 is preferably'lo 1 ever the starting igniter-12 is in operation, and cated in theairplane cabin within convenient that-the lamp 86 will automaticallyextinguish reach of the pilot. The other condl'zlctorv leading eneverthe electrical circuit through the igniter from the power source extendsinto connected -is-opened.- I

relation with a pi-metallic cantilever arm I! which is mounted uponthe-casing structure and carry that the pilot move the switch I. to

To stop the heater operation, it is only necesis so formed as to bear,under normal tempera- '70 heater-off position, whereupon the circuit tothe ture conditions, in electrically contacting mansolenoid controlledvalve 58 will be opened so as to. ner t; t lunflxed end portion againsta c ncause the valve to return to closed position. 81-.

tact element ,84 from which a. conductor leads multaneouslm'the irhrough the fan motor into operative connection with one end of' the 5 Wbe opened to, discontinue s pply of D l resistance wire element of thestarting igniter to the fan. Uporr subsequentcooling. of the becomesaccidentally cut, as by a shot during combat, the supply of fuel vaporto the combustion chamber will be discontinued and the temperaturethereof will thus lower to such a point that the bi-metallic arm 82 willdisconnect from.

the contact 90 and reconnect with the contact 84. Thus the fan will stopand the signal lamp 86 will be energized to warn the pilotof thedisruption to the system, so that he may open the switch 80 to cause thevalve I8 to close.

As a result of experiments we have found that it is to be preferred toprovide against too rapid removal of the fuel vapor and products ofcombustion from the combustion chamber 40, and for this purpose weprefer to provide a restriction in the .line of the discharge conduit62. For example, a perforated disc 15 may be disposed at connection withpartial vacuum sou ces such as the intake manifold of a standard typeinternal combustion engine. In such cases the apparatus is entirelyunsuited to operation at substantial altitudes such as at which modemairplanes are I called upon to operate. For example, a heater of thistype of the prior art has been tested-for possible use as an airplaneaccessory and it ceased operation at altitudes around seven to ten thousand feet above sea level. As distinguished from the above, theapparatus of the invention is adapted to function at altitudes up totwenty the point of seating of the connection nipple Bl in the header50; the disc 1;! being formed with a small central opening so as topermit flow of gases therethrough at a predetermined reduced rate.Consequently, the fuel vaporis caused to thousand feet above sea levelwith facility equal to that of its operation at sea level. As the alti-'tude increases above twenty thousand feet the pressure differential ofthe, system slowly decreases and approaches zero as the absolute ceilingof the airplane is reached. Consequently, the apparatus is effective forall practical p p ses under all operating conditions to be met with inconnection with the use of the airplane.

In another form of the invention the conduit 62 may be arranged todirect the heater discharge gases into the atmosphere externally of theairplane engine fuel intake system. In such case aiiplanefuselage'insuch manner that an additlonal pressure differential will thereby be generated to assist in the induction of fuel flow through the heat exchangesystem.

change efliciency is obtained in connection withv 1 positive fuelfeeding action under all operating conditions of the airplane andwithout regard to the altitude at which the airplane is operating,

up to the absolute ceiling altitude of the airplane e ine.-

Thus, it will be understood that the positive pressure conditiongenerated within the intake manifold 22 of the airplane engine inresponse to operation of the blower 20 is at all times considerably inexcess of the atmospheric pressure externally of the airplane fuel feedsystem and of the pressure within theengine fuel conduit '6.Consequently, the fuel vapor is introduced into the conduit 54 of theheater system and is induced to flow into thecombustion chamber 40',while the products of combustion or other discharge gases are similarlyinduced to,flow out of the combusj tion chamber through the dischargeconduit without other assistance. It will be appreciated that the heatervapor circulating system and the engine fuel feed system combine toprovide a closed fluid handling system which is separated from theatmosphere externally of the airplane.

, Consequently, the functioning of the heater apheater, a conduit forsupplying combustible mixof fuel and air, the combination of an internalAlthough the invention has been illustrated and described hereinabove inan exemplary manner L I only, itwill be understood by those skilled inthe art that the invention is not so limited but that various changesmay be-made therein without with an internalcombustion engine receivinga compressed combustible mixture of fuel and air from a superchargerhaving an inlet and an outlet, the combination of an internal combustionture to saidheater from said outlet, and a conduit for discharging theproducts of combustion from said heater into said inlet, whereby thedifferential pressure created by said supercharger will causecombustible mixture to flow to said heater, and the products ofcombustion to flow therefrom 2. ma heating, system for use inconjunction with an internal combustion engine having a superchargercompressing a combustible mixture combustion heater having a combustionchamher and a heat exchanger receiving the products of. combustiontherefrom, a duct for supplying combustible mixture to, saidcombustion-chamber from a point at which combustible mixture has beencompressed by said superchargenand a duct for conveyin said products ofcombustion from said heat exchanger to a point where combustiblemixtureis maintained at a pressure less than at said first-named point by theaction of said supercharger. 5

FRANK M. SALISBURY.

8. LA BEA.

